This is Steven Salzberg's blog on genomics, pseudoscience, medical breakthroughs, higher education, and other topics, including skepticism about unscientific medical practices. Here's where I can say what I really think about abuses and distortions of science, wherever I see them.

A European Union court just issued a new decision about GMOs. Disappointingly, this decision is likely to confuse rather than clarify this complex and contentious issue. The court announced that plants whose genomes have been modified with CRISPR technology, a very precise form of genome editing, are subject to the EU's very strict restrictions on genetically modified crops.

If we take this literally, then here’s a list of all the foods that have never been subjected to mutagenesis, and are therefore NOT GMO:

Salt

Wild boar

Wild blueberries

That’s it. (OK, maybe there are a few others.)

We have been modifying the genes of the foods we eat for millenia. Every loaf of organic, non-GMO bread is made from wheat that humans have modified since ancient times. Every glass of milk from your grass-fed, bovine-growth-hormone-free cow comes from a cow that humans have bred for centuries. All cows are genetically modified. Those delicious croissants you bought at the organic bakery? Sorry, those are GMOs, no matter how organic you think they are.

And corn? Have you seen what ancient corn, called teosinte, looks like? I encourage you to Google it (or see the image on this blog, above). Modern corn is the result of many generations of human-driven genetic modifications.

To be fair, the EU court recognized that many of our foods have been genetically modified for a long time, and that it might be impractical to remove all of them from our food supply. So they carved out an exception:

"varieties [of plants] obtained by means of mutagenesis techniques which have conventionally been used in a number of applications and have a long safety record are exempt...."

What's ironic here–though I'm confident that the EU court didn't mean this–is that by this definition, virtually all of the GMO crops in the U.S. are exempt. You see, we've been eating them for decades, and they have a phenomenal safety record.

Two years ago, the US National Academies of Sciences, Engineering, and Medicine issued a massive report that reviewed over 1,000 studies of GMOs. The bottom line: there are no health risks whatsoever from eating genetically modified foods.

Earlier gene editing technology sometimes added foreign genes to an organism, such as adding a bacterial gene to a plant. The EU court's new decision is intended to clarify that even if a foreign gene is not involved, plants bred using the newest form of gene editing (CRISPR technology) are nonetheless GMOs.

Banning GMOs doesn't make sense, and it never did. Genetic technology is just a tool, one that can be used for countless purposes, some of them highly beneficial–such as golden rice, which has the potential to prevent blindness in countries where many people depend on rice as their main staple food. If someone objects to a particular use of GM technology, such as Monsanto's use of it to create herbicide-resistant plants, that's something we can reasonably debate. But banning all GMOs is throwing out the baby with the bathwater.

Now if you'll excuse me, I've got to go out to my grill and see how my wild boar is doing. It might need a bit more salt.

I thought we'd put this one to bed. A large-scale study showed that low-dose aspirin (one quarter of a standard 325 mg pill, or about 81 mg) taken once a day can prevent heart attacks and some common types of cancer, including colon cancer.

But now, a new study just published in The Lancet upends that advice. It's not that the previous study was wrong–it wasn't. It's just that the effects of aspirin vary significantly based on body weight. Essentially, the new study finds, almost all of the benefits accrue to people who weigh 70 kilograms (154 pounds) or less.

The study, a re-analysis by Peter Rothwell and colleagues of ten large trials that included 117,279 participants, is too long and complex to summarize here, so I'll just highlight a few key points. (Because the paper is open access, anyone can read it for free, just by clicking here.)

The good news, for people who weigh between 50 and 70 kg (110-154 lbs), is that the benefits of daily low-dose aspirin are quite good, possibly even better than we thought. The relative risk of a heart attack, stroke, or other major heart-related event is about 25% lower for people in this group.

The bad news, for the rest of us, is that we seem to get no heart-related benefits from taking a daily low-dose aspirin.

So perhaps those of us who weigh more than 70 kg just need a slightly larger daily aspirin pill. There is some good news here: Rothwell and colleagues found that, indeed, higher doses of aspirin are effective at reducing the risk of heart attacks for people who weigh more than 70 kg. This makes sense: adjusting the dosage based on weight is how most drugs are given. The problem is that aspirin generally comes in only 3 pill sizes: 81, 325, and 500 mg. So the studies have only looked at these 3 doses, and 325 mg is likely too large a dose for most people, because it increases the risk of bleeding events.

What about the cancer risk? As I wrote in 2017, the biggest benefit from daily low-dose aspirin is its reduction in the risk of colon cancer, breast cancer, and prostate cancer. Here, the new study doesn't quite give the whole picture, because it didn't look at breast cancer or prostate cancer. For colon cancer, low-dose aspirin reduces the risk significantly for people who weigh less than 70 kg. For heavier people, low-dose aspirin had little to no effect on colon cancer risk, but regular-sized aspirin (325 mg) worked for people up to 80 kg (176 lbs).

What to do now? The new study concludes that:

"The one-dose-fits-all strategy for daily aspirin use is unlikely to be optimal."

In other words, you will probably benefit from daily aspirin, but the amount you should take depends on your weight. If you weigh less than 70 kg, the 81-mg tablets that you can find almost anywhere will do nicely.

But what if you weigh more (as most men and many women do)? The science doesn't yet give us an answer: you could simply take 2 low-dose pills a day, but too much aspirin increases the risk of serious bleeding events. You could instead take a few extra pills per week, depending on your weight, which is what I'm going to do, at least until we get better data and more precise guidelines.

(Final note: as always, before you make any changes in your medication, ask your physician.)

It's summer time, and with it comes outdoor dining, sports, and strolls through the neighborhood. But the loveliest evening can be spoiled by mosquitos, who torment us as they suck our blood and leave itchy welts behind.

How can we keep these pests away? Do citronella candles work? How about Victoria's Secret Bombshell perfume? (No, I'm not kidding. Read on.)

First, about mosquitos: they are more than just a nuisance. They also carry diseases, including West Nile virus, which now affects the entire U.S., and far more deadly diseases in other countries, including malaria, yellow fever, and Zika virus.

One of the most popular ways to keep mosquitos off the backyard patio is easy to spot on a summer night in my neighborhood: burning citronella candles (such as this one from Cutter), which contain a natural oil made from grass whose scent is supposed to repel mosquitos. These are very popular and widely sold, but do they work?

Here's the setup: the scientists placed a cage full of mosquitos near a human volunteer, who sat 1-3 meters away, with a gentle breeze blowing from the humans towards the mosquitos. (This made it easier for the mosquitos to smell the humans, and also meant that they had to fly against the breeze if they wanted to bite the subjects.) The scientists applied each mosquito repellent (or device) to the volunteers, opened the cage, and counted how many mosquitos were attracted. They also ran controls where the subject had no protection.

Nothing else worked nearly as well as these, although several products reduced the proportion of mosquitos from 88% down to 60-70%.

Notably, some of the products did not work at all, including citronella: Cutter Citro Guard had no effect on the mosquito's attraction to the human volunteers. Other failures were Invisaband™ and Mosquitavert, wrist bracelets containing geraniol oil, and the PIC® Personal Sonic Mosquito Repeller, a clip-on ultrasonic device that emits a sound that mosquitos presumably don't like. Mosquitos basically ignored these devices.

So what's the secret in the products that do work? The OFF! device contains metofluthrin, which appears to be the most effective repellent on the market. Lemon eucalyptus oil is a natural product that is nearly as effective, and Ben's Tick & Insect Repellent contains DEET, which has long been known as an effective defense against mosquitos.

The only one of these products that purports to work on a whole area (like your backyard patio) rather than just one person is the citronella candle, which unfortunately just doesn't work. So if you want your garden party guests to be protected, you may have to keep on hand a basket full of products with metofluthrin, lemon eukalyptus oil, or DEET.